Insulin C-peptides

ABSTRACT

The invention features peptides that are fragments of the human insulin C-peptide, which peptides include the sequence ELGGGPGAG or a fragment thereof, or the sequence EGSLQ or a fragment thereof. The peptides have the ability to stimulate Na + K + ATPase activity. Also provided are biomimetic organic compounds exhibiting activation of Na + K + ATPase activity and/or cellular binding to renal tubule cells and fibroblasts. Such peptides and compounds are useful in combating diabetes and diabetic complications, or for stimulating Na + K + ATPase activity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Swedish Application Serial No. 9603533-2, filed on Sep. 27, 1996, and PCT International Application No. PCT/GB97/02627, filed on Sep. 26, 1997.

FIELD OF THE INVENTION

The present invention relates to fragments of the insulin C-peptide and their use in the treatment of diabetes and diabetic complications.

BACKGROUND

Patients with insulin-dependent diabetes mellitus (IDDM), generally synonymous with type 1 diabetes, cannot survive without insulin therapy. IDDM is the classical, life-threatening form of diabetes, the treatment of which was revolutionized by the discovery of insulin in 1922. The prevalence of IDDM in Europe, North America and Japan is 0.25-0.4% of the population. There is a seasonal variation in the incidence of IDDM with more patients presenting in the autumn and winter months. The disorder affects a slight excess of males but this difference becomes less marked with increasing age.

The classical symptoms of IDDM in its acute phase are thirst, large urine volumes, fatigue and weight loss. Less frequent and minor symptoms are muscle cramps, skin infections and blurred vision. Nausea and vomiting may occur in advanced stages and denote impending ketoacidosis and coma. The duration of symptoms is short, usually 2-3 weeks or less. The patients present with high concentrations of glucose and ketone bodies in blood and urine while insulin levels are low or undetectable.

The etiology of IDDM is multifactorial but most likely includes a genetic predisposition for autoimmune reactivity together with environmental triggering, possibly via a virus infection, resulting in partial or complete destruction of the pancreatic beta cells. The destruction of beta cells may have been in progress during the 6-12 months preceding the onset of the disorder. In the acute phase of IDDM insulin deficiency is thus the dominating pathophysiological feature.

After starting insulin treatment many patients enjoy good blood glucose control with only small doses of insulin. There is an early phase, the “honeymoon period”, which may last a few months to a year and which probably reflects a partial recovery of beta cell function. This is, however, a temporary stage and ultimately, the progressive autoimmune destruction of the beta cells leads to increasing requirements for exogenous insulin.

While the short term effects of hypoinsulinemia in the acute phase of IDDM can be well controlled by insulin administration, the long term natural history of IDDM is darkened by the appearance in many patients of potentially serious complications. These include the specifically diabetic problems of nephropathy, retinopathy and neuropathy. These conditions are often referred to as microvascular complications even though microvascular alterations are not the only cause. Atherosclerotic disease of the large arteries, particularly the coronary arteries and the arteries of the lower extremities, may also occur.

Nephropathy develops in approximately 35% of IDDM patients particularly in male patients and in those with onset of the disease before the age of 15 years. The diabetic nephropathy is characterized by persistent albuminuria secondary to glomerular capillary damage, a progressive reduction of the glomerular filtration rate and eventually, end stage renal failure.

The prevalence of diabetic retinopathy is highest among young-onset IDDM patients and it increases with the duration of the disease. Proliferative retinopathy is generally present in about 25% of the patients after 15 years duration and in over 50% after 20 years. The earliest lesion of diabetic retinopathy is a thickening of the capillary basement membrane, there is then capillary dilatation and leakage and formation of microaneurysms. Subsequently, occlusion of retinal vessels occurs resulting in hypoperfusion of parts of the retina, oedema, bleeding and formation of new vessels as well as progressive loss of vision.

Diabetic neuropathy includes a wide variety of disturbances of somatic and autonomic nervous function. Sensory neuropathy may cause progressive loss of sensation or, alternatively, result in unpleasant sensations, often pain, in the legs or feet. Motor neuropathy is usually accompanied by muscle wasting and weakness. Nerve biopsies generally show axonal degeneration, demyelination and abnormalities of the vasa nervorum. Neurophysiological studies indicate reduced motor and sensory nerve conduction velocities. Autonomic neuropathy afflicts some 40% of the patients with IDDM of more than 15 years duration. It may evolve through defects in thermoregulation, impotence and bladder dysfunction followed by cardiovascular reflex abnormalities. Late manifestations may include generalized sweating disorders, postural hypotension, gastrointestinal problems and reduced awareness of hypoglycemia. The latter symptom has grave clinical implications.

Several theories have been advanced with regard to possible mechanism(s) involved in the pathogenesis of the different diabetic complications (1). Metabolic factors may be of importance and recent studies demonstrate that good metabolic control is accompanied by significantly reduced incidence of complications of all types (2). Nevertheless, after 7-10 years of good metabolic control as many as 15-25% of the patients show signs of beginning nephropathy, 10-25% have symptoms of retinopathy and 15-20% show delayed nerve conduction velocity indicating neuropathy. With longer duration of the disease the incidence of complications increases further.

C-peptide is a part of the proinsulin molecule which, in turn, is a precursor to insulin formed in the beta cells of the pancreas. Human C-peptide is a 31 amino acid peptide having the following sequence: EAEDLQVGQVELGGGPGAGSLQPLALEGSLQ (SED ID. NO. 1). It has been suggested in EP 132 769 that C-peptide may be given for the treatment of diabetes and in SE 460334 that insulin in combination with C-peptide can be administered in the treatment of diabetes and in the prevention of diabetic complications.

In recent years it has become apparent that type 1 diabetes is accompanied by consistently reduced activity of the enzyme Na⁺K⁺ATPase in several tissues, notably in renal glomeruli, retina, peripheral nerve, heart and skeletal muscle (3, 4, 5). Na⁺K⁺ATPase is an enzyme that is localized to the cell membrane and generates energy for transcellular transport of Na⁺ and K⁺ as well as for all co- or countertransported substrates in all mammalian cells. It is thus obvious that the activity of this enzyme is of fundamental importance for normal cell function. Deficient Na⁺K⁺ATPase activity in nervous tissue, glomeruli and retina is likely to be an important contributing factor in the pathogenesis of diabetic neuropathy, nephropathy and retinopathy. Na⁺K⁺ATPase activity is regulated via the Na⁺ concentration and by hormonal action; several hormones stimulate (thyroid hormone, noradrenalin, angiotensin, neuropeptide Y, insulin) or inhibit (dopamine, ANF) the enzyme's activity (6). Despite insulin treatment sufficient to achieve good glycemic control, patients with type 1 diabetes show signs of insufficient Na⁺K⁺ATPase activity on a long term basis.

BRIEF SUMMARY OF THE INVENTION

The present invention is based on the discovery of a group of peptides from the middle portion and the C-terminal part of the C-peptide molecule which are characterized by a remarkable ability to stimulate Na⁺K⁺ATPase activity. These peptides are all small fragments of the C-peptide molecule. C-peptide itself is able to stimulate Na⁺K⁺ATPase via activation of a G-protein, increase in the intracellular Ca²⁺ concentration and activation of protein phosphatase 2B (7). However, the smaller peptides' stimulatory effect on Na⁺K⁺ATPase activity is similar to or greater than that of C-peptide itself. There is both in vitro and in vivo evidence to indicate that upon administration of one of these peptides together with regular insulin treatment, renal function improves, early signs of retinopathy regress and the function of somatic and autonomic nerves improves. Treatment with these specific peptides, optionally in combination with conventional insulin therapy is thus useful in preventing or substantially retarding the development of late diabetic complications. A potential advantage that the small peptides possess over C-peptide is that they may be administered orally instead of by injection as in the case of C-peptide and insulin.

In one aspect, the present invention thus provides a peptide being a fragment of the human insulin C-peptide, said peptide comprising the sequence ELGGGPGAG (SEQ ID NO. 2) (hereinafter “peptide A”) or a fragment thereof, or the sequence EGSLQ (SED ID NO. 3) (hereinafter “peptide E”), or a fragment thereof, and having the ability to stimulate Na⁺K⁺ATPase activity.

In a more particular embodiment, the present invention provides a peptide having the sequence ELGGGPGAG (SEQ ID NO. 2) or EGSLQ (SEQ ID NO. 3), or a fragment thereof.

Especially, the invention provides such peptides for use in therapy and more particularly for use in combatting diabetes and diabetic complications.

In another aspect the present invention provides a pharmaceutical composition comprising a peptide of the invention or a fragment thereof as hereinbefore defined together with at least one pharmaceutically acceptable carrier or excipient.

A yet further aspect of the present invention provides the use of a peptide of the invention, or a fragment thereof, as hereinbefore defined, in the manufacture of a medicament for combatting diabetes or diabetic complications.

As used herein the term “combatting” includes both treatment and prophylaxis.

The present invention thus relates to the use of the following peptides which all are fragments of C-peptide: Peptide A (amino acid sequence ELGGGPGAG) (SEQ ID NO. 2) or components thereof, for example Peptide B (ELGG)(SEQ ID NO. 4), Peptide C (ELGGGP) (SEQ ID NO. 5) or Peptide D (GGPGA) (SEQ ID NO. 6). In addition, the invention includes Peptide E (EGSLQ)(SEQ ID NO. 3) and parts thereof, for example Peptide F (GSLQ) (SEQ ID NO. 7). All are intended for the manufacture of a medicament for treating type 1 diabetes.

Fragments of the invention have been proven to stimulate Na⁺K⁺ATPase activity to varying extent. Thus, studies involving renal tubule cells under in vitro conditions indicate that Peptides A-D stimulate Na⁺K⁺ATPase activity to an extent comparable to that for the whole C-peptide molecule. As much as 90% of the effect is achieved within 3 minutes. Moreover, Peptides E and F possess a stimulatory effect on Na⁺K⁺ATPase of renal cells which is comparable to or greater than that for the whole molecule. Combinations of Peptides A-D with Peptides E or F result in a stimulation of the enzyme activity that is greater than that for either peptide alone. For detailed examples of the stimulatory effects of the above peptides, see Example 1, below.

C-peptide exhibits specific binding to the surface of several cell types, notably renal tubule cells and fibroblasts. When fluorescently labelled C-peptide is incubated with cells it binds to the cell surface. The specificity of the binding is illustrated by the fact that preincubation with unmarked C-peptide prevents binding of the fluorescently labelled C-peptide. When preincubation with the fragments of the invention, particularly with either of fragments E or F was made, the fragments were found to prevent binding of the fluorescently marked C-peptide, demonstrating that the fragments bind specifically to the same binding site on the cell surface as C-peptide itself. For a detailed example of the binding of Fragment E see Example 28, below.

As mentioned above, included within the scope of the invention are peptides comprising the sequences of not only peptides A and E, but also their fragments. In the case of the nonapeptide A, such fragments may be 8 to 2 amino acids in length. In the case of the pentapeptide peptide E, such fragments may be 4 to 2 amino acids in length. Exemplary fragments B, C and D (for peptide A) and F (for peptide E) are listed above, but other fragments are also included.

In the case of peptide A certain studies on Na⁺K⁺ATPase activity, studying the ability of the peptide fragments to stimulate the activity of Na⁺K⁺ATPase of rat renal tubule segments, have shown that one or more of the central tri-glycine residues may be important, and preferred peptide fragments, where peptide A is concerned, thus include at least one, and more preferably, at least two, of the central tri-glycine residues. Thus, in addition to peptides B, C and D mentioned above, representative exemplary peptide fragments include GGGPGAG (SEQ ID NO. 8), GGGPG (SEQ ID No. 9), GGGP (SEQ ID NO. 10), GGP and GGPG (SEQ ID NO. 11).

Furthermore, it has been found that peptides containing non-natural D-amino acid isomers may also be active, including for example the dipeptide D-LG or D,L-LG. Thus, included within the scope of the invention are “non-native” isomers of the “native” L-amino acid C-peptide sequences. Insofar as peptide A is concerned, it is believed that the presence of at least one (if D-peptide) or two (if L-peptide) of the central tri-glycine residues may be important in a 9 amino acid or less peptide segment.

In the case of peptide E, exemplary representative fragments include not only the tetrapeptide, peptide F, but also SLQ and LQ. The C-terminal Q residue is believed to be of importance. Likewise, non-native isomers or derivatives of the peptides e.g. peptides including D-amino acids are included within the scope of the invention.

The invention encompasses peptides comprising the sequences of peptides A and E. Thus, also included within the scope of the invention are peptides having N- and/or C-terminal extensions, or flanking sequences, to the sequences of peptides A and C. Such peptides may include additional amino acids which may either be those provided in the corresponding position in the native human insulion C-peptide or other amino acids (excluding of course the possibility of reconstituting the entire insulin C-peptide). The length of such “extended” peptides may vary, but preferably the peptides of the invention are no more than 25 or 20, especially preferably not more than 15 or 10 amino acids in length. Exemplary peptides include octa-, hepta and hexa-peptides including the sequence of peptide E, e.g. LALEGSLQ (SEQ ID NO. 12), ALEGSLQ (SEQ ID NO. 13) and LEGSLQ (SEQ ID NO. 14).

The peptides of the invention can be used for the treatment of diabetes and diabetic complications, most notably type 1 diabetes and its complications. As used herein the term “diabetic complications” thus includes all complications known in the art to be associated with various forms of diabetes. Whilst not wishing to be bound by theory, the utility of the peptides is believed, as explained above, to be linked to their ability to stimulate Na⁺K⁺ATPase activity. A further aspect of the invention thus includes the peptides for use in, and their use in preparing medicaments for use in stimulating Na⁺K⁺ATPase activity in a subject.

Na⁺K⁺ATPase activity may readily be assayed using techniques known in the art and described in the literature and thus the effect of the peptides in stimulating Na⁺K⁺ATPase activity may readily be determined (for example, see reference 7).

Thus, the peptides can be used for the manufacture of a medicament for stimulation of Na⁺K⁺ATPase activity, for treating type 1 diabetes patients with retinopathy, for treating type 1 diabetes patients with nephropathy, for treating type 1 diabetes patients with neuropathy and for retarding the development of late diabetic complications. The medicament may comprise insulin. The invention also relates to the method for treatment or prevention of the above given indications.

The peptides of the invention may be used singly or in combination and thus a pharmaceutical composition or medicament may be prepared comprising one or more of the peptides. As mentioned above, a synergy has been observed between peptide A or peptides based on or derived from peptide A (the “peptide A group”) and peptide E or peptides based on or derived from peptide E (the “peptide E group”). Thus, synergistic combinations of a peptide from the peptide A group, with a peptide from the peptide E group represent a preferred embodiment of the invention.

The peptides may also be used in combination or conjunction with other agents active or effective to treat diabetes and/or its complications. Such other active agents include for exammple insulin. In such “combination” therapies the peptide(s) and second active agent may be administered together in the same composition or separately in separate compositions, simultaneously or sequentially.

A further aspect of the invention thus provides a product containing a peptide of the invention, or a fragment thereof, as hereinbefore defined together with a further active agent effective to combat diabetes or diabetic complications, as a combined preparation for simultaneous, separate or sequential use in combatting diabetes and/or diabetic complications. Preferably such a further active agent is insulin.

In such combined therapies, where insulin is used, it is to be understood that the term “insulin” encompasses all forms, types and derivatives of insulin which may be used for therapy e.g. synthetic, modified, or truncated variants of the active human insulin sequence.

The compositions of the invention may be administered orally or parenterally by the subcutaneous, intramuscular or intravenous route. The compositions of this invention comprise active fragments/peptides of the C-peptide molecule (e.g. Peptides A-F), together with a L pharmaceutically acceptable carrier therefor and optionally, other therapeutic ingredients, for example human insulin. The total amount of active ingredients in the composition varies from 99.99 to 0.01 percent of weight. The carrier must be acceptable in the sense that it is compatible with other components of the composition and is not deleterious to the recipient thereof.

The compositions may be formulated according to techniques and procedures well known in the art and widely described in the literature, and may comprise any of the known carriers, diluents or excipients. Thus, for example, compositions of this invention suitable for parenteral administration conveniently comprise sterile aqueous solutions and/or suspensions of the pharmaceutically active ingredients (e.g. Peptides A-F) preferably made isotonic with the blood of the recipient, generally using sodium chloride, glycerin, glucose, mannitol, sorbitol, and the like. In addition, the compositions may contain any of a number of adjuvants, such as buffers, preservatives, dispersing agents, agents that promote rapid onset of action or prolonged duration of action and the like.

Compositions of this invention suitable for oral administration may, for example, comprise active fragments/peptides of the C-peptide molecule (e.g. Peptides A-F) in sterile purified stock powder form preferably covered by an envelope or envelopes (enterocapsule) protecting from degradation (decarboxylation or hydrolysis) of the active peptides in the stomach and thereby enabling absorption of these substances from the gingiva or in the small intestine. The envelope(s) may contain any of a number of adjuvants such as buffers, preservative agents, agents that promote prolonged or rapid release giving an optimal bioavailability of the compositions in this invention, and the like.

In addition, the present invention relates to non-peptide compounds showing the same stimulatory effects as displayed by their C-peptide-derived counterparts. Such peptidomimetics or “small-molecules” capable of mimicking the activity of the naturally occurring proteins or peptides are likely to be better suited for e.g. oral delivery due to their increased chemical stability (8,9).

It is now commonplace in the art to replace peptide or protein-based active agents e.g. therapeutic peptides with such peptidomimetics having functionally-equivalent activity. Various molecular libraries and combinatorial chemistry techiques exist and are available to facilitate the identification, selection and/or synthesis of such compounds using standard techniques (10). Such standard techniques may be used to obtain the peptidomimetic compounds according to the present invention, namely peptidomimetic organic compounds which show substantially similar or the same activation of Na⁺K⁺ATPase and/or cellular binding characteristics as the peptides of the invention, e.g. as described herein in the Examples.

A further aspect of the invention thus provides a biomimetic organic compound based on the peptides of the invention, characterised in that said compound exhibits activation of Na⁺K⁺ATPase and/or cellular binding characteristics to renal tubule cells and fibroblasts at at least the level exhibited by the peptides and peptide fragments of the invention as hereinbefore defined.

DESCRIPTION OF THE DRAWING

The invention will now be described in more detail in the following non-limiting Examples which show, inter L alia, the stimulatory effect of specific peptides on Na⁺K⁺ATPase activity, and cell-binding with reference to the drawing in which:

FIG. 1 shows a chromatogram from a preparative reverse phase purification of human C-peptide labelled with tetramethylrhodamine. The column was eluted with a 20 to 40% acetonitrile gradient (acetonitrile in 0.1% trifluoroacetic acid (TFA) during 20 minutes. Peak A corresponds to unreacted fraction of C-peptide. Peaks B and C correspond to C-peptide labelled with tetramethyl-rhodamine. The separation of the B and C peaks corresponds to the presence of two tetramethylrhodamie isomers in the activated reagent. For further studies material from the C-peak was used. Solid line corresponds to absorbtivity at 220 nm (peptide) and dashed line to absorbtivity at 555 nm (tetramethylrhodamine).

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1

The stimulatory effect of Peptides A-F on Na⁺K⁺ATPase activity of rat renal tubule cells was examined. Single proximal convoluted tubules were prepared from rat kidneys by micro-dissection. The tubules were incubated for 30 minutes at room temperature with either of Peptides A-F or rat C-peptide 1. Na⁺K⁺ATPase activity was then measured following exposure of the tubules to hypotonic shock and incubation for 15 minutes in a medium containing ³²P-ATP in the presence or absence of oubain.

The stimulatory activity of 5-10⁻⁷ M rat C-peptide 1 was set at 100%. For the same concentration of Peptides A-F the following relative activities were obtained:

Peptide A 88±3 percent

Peptide B 36±2 percent

Peptide C 46±3 percent

Peptide D 65±4 percent

Peptide E 110±3 percent

Peptide F 96±2 percent

Peptides B+C 86±3 percent

Examples of particular pharmaceutical compositions of this invention are provided in the examples below.

EXAMPLE 2

Human Insulin: Peptide A alone or in equimolar mixture with Peptides B, C, D, E and F (1:4 on a molar basis at 100 Units M insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide A alone—16.8 mg

M-Kreosol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition vloume of 10 ml and a final pH of 7.0-7.8 or a combination with

Peptide A—16.8 mg

Peptide B—8.8 mg

Peptide C—13.6 mg

Peptide D—10 mg

Peptide E—12.4 mg

Peptide F—9.2 mg

M-Kresol—25 mg

Glycerol—160 mg

Water and either 10%—hydrochloride acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 3

Human Insulin: Peptide B (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide B—8.8 mg

M-Kresol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloride acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.7-7.8

EXAMPLE 4

Human Insulin: Peptide C (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide C—13.6 mg

M-Kresol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloride acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 5

Human Insulin: Peptides D (1:5 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide D—10.0 mg

M-kreosol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloride acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 6

Human Insulin: Peptide E (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide E—12.4 mg

M-Kresol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 7

Human Insulin: Peptide E (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human insulin (28 U/mg)—1000 U

Peptides F—9.2 mg

M-Kreosol—25 ml

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 8

Human Insulin: Peptide A alone or mixed equimolar together with fragments B, C, D, E and F (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide A—4.2 mg

M-Kreosol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8 or a combination with

Peptide A—4.2 mg

Peptide B—2.2 mg

Peptide C—3.4 mg

Peptide D—2.5 mg

Peptide E—3.1 mg

Peptide F—2.3 mg

M-Kreosol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 9

Human Insulin: Peptide B (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide B —2.2 mg

M-Kreosol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 10

Human Insulin: Peptide C (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide C—3.4 mg

M-Kieosol—25 ml

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 11

Human Insulin: Peptide D (1:1 on a molar basis at 1000 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide D—2.5 mg

M-Kreosol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloric acid of 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 12

Human Insulin: Peptide E (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide E—3.1 mg

M-Kreosol—25 mg

Glycerol—160 ml

Water and either 10% hydrochloric acid of 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 13

Human Insulin: Peptide E (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin (28 U/mg)—1000 U

Peptide F—2.3 mg

M-Kreosol—25 mg

Glycerol—160 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.0-7.8

EXAMPLE 14

Human Zinc Insulin: Peptide A alone or mixed equimolar together with fragments B, C, D, E and F (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst

700 U (28 U/mg)—1000 U

Peptide A—16.8 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4 or a combination with

Peptide A—16.8 mg

Peptide B—8.8 mg

Peptide C—13.6 mg

Peptide D—10 mg

Peptide E—12.4 mg

Peptide F—9.2 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric sodium hydroxide sufficient to make a composition volume and a final pH of 7.1-7.4

EXAMPLE 15

Human Zinc Insulin: Peptide B (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide B—8.8 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide suficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 16

Human Zinc Insulin: Peptide C (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide C—13.6 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hyrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 17

Human Zinc Insulin: Peptide D (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide D—10.0 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid of 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 18

Human Zinc Insulin: Peptide E (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 and modific cryst 700 U

(28 U/mg)—1000 U

Peptide E—12.4 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid of 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 19

Human Zinc Insulin: Peptide F (1:4 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide F—9.2 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid of 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 20

Human Zinc insulin: Peptide A alone or mixed equimolar together with fragments B, C, D, E and F (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide A—4.2 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4 or a combination with

Peptide A—4.2 mg

Peptide B—2.2 mg

Peptide C—3.4 mg

Peptide D—2.5 mg

Peptide E—3.1 mg

Peptide F—2.3 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid of 10% sodium hudroxide suffient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 21

Human Zinc Insulin: Peptide B (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide B—2.2 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid of 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 22

Human Zinc Insulin: Peptide C (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide C—3.4 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 23

Human Zinc Insulin: Peptide D (1:1 on a molar basis at 100 Units (U) insulin per ml).

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide D—2.5 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid or 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 24

Human Zinc Insulin: Peptide E (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide E—3.1 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid or 10 sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 25

Human Zinc Insulin: Peptide F (1:1 on a molar basis at 100 Units (U) insulin per ml).

To prepare 10 ml of the composition, mix

Human Insulin in modific amorph 300 U and modific cryst 700 U

(20 U/mg)—1000 U

Human Insulin in modific amorph 300 U and modific cryst 700 U

(28 U/mg)—1000 U

Peptide F—2.3 mg

Zinc—1.3 mg

Sodium chloride—70 mg

Sodium Acetate—16 mg

Methyl Parahydroxybenz—10 mg

Water and either 10% hydrochloric acid of 10% sodium hydroxide sufficient to make a composition volume of 10 ml and a final pH of 7.1-7.4

EXAMPLE 26

Peptide A

To prepare sublingual tablets of enterocapsules each containing the composition equimolar to 100 U of insulin, mix

Peptide A—0.42 mg

Lactos—30 mg

et const q s

or in combination of Peptide A: Peptide B: Peptide C: Peptide D: Peptide E: Peptide F: (1:1:1:1:1:1 on molar basis)

To prepare sublingual tablets of enterocapsulas each containing the composition equimolar to 100 U of insulin, mix

Peptide A—0.42 mg

Peptide B—0.22 mg

Peptide C—0.34 mg

Peptide D—0.25 mg

Peptide E—0.31 mg

Peptide F—0.23 mg

Lactos—30 mg

et const q s

EXAMPLE 27

Peptide A

To prepare sublingual tablets or enterocaplulas each containing the composition equimolar to 400 U of insulin, mix

Peptide A—1.67 mg

Lactos—30 mg

et const q s

or in combination of Peptide A: Peptide B: Peptide C: Peptide D: Peptide E: Peptide F (1:1:1:1:1:1 on molar basis)

To prepare sublingual tablets or enterocapsulas each containing the composition equimolar to 400 U of insulin, mix

Peptide A—1.68 mg

Peptide B—0.88 mg

Peptide C—1.36 mg

Peptide D—1.0 mg

Peptide E—1.24 mg

Peptide F—0.92 mg

Lactos—30 mg

et const q s

EXAMPLE 28

The specific binding of Peptide E to the cell surface is illustrated as follows. Human biosynthetic C-peptide (Eli-Lilly, Inc., Indianapolis, USA) was labelled with tetramethylrhodamine using the activated reagent tetramethylrhodamine succinimidyl ester (FluoReporter® Protein labelling kit, Art. no. F-6163; Molecular Probes Europe BV, Leiden, Netherlands). The coupling reaction was performed at pH 8.3 (0.1 M NaHCO₃ buffer) with a five-fold stoichiometrical excess of activated reagent to C-peptide. The tetramethylrhodamine group has absorption/emission maxima at 555/580 nm, respectively and is incorporated in the N-terminus of the C-peptide. Labelled C-peptides were purified by gel filtration (desalting against 50 mM phosphate buffer, 0.1 M NaCl, pH 7.4) on a NAP-5 column; Pharmacia Biotech Uppsala, Sweden) and subsequently by preparative reverse phase chromatography (250 mm Kromasil C8 column, diam. 4.6 mm, 7 μm particle size, 10 nm pore size, Eka-Nobel, Surte, Sweden) using a 1090 Hewlett Packard HPLC chromatography system (Grenoble, France) (FIG. 1). Eluted material was immediately adjusted to pH 8 by addition of ammonia and subsequently lyophilized.

Cultured human renal tubule cells (proximal convoluted tubules, PCT) were incubated with the rhodamine labelled C-peptide synthesized as described above. The cells were prepared from the healthy part of a human kidney removed surgically because of hypernephroma. The outer 150 μm of the renal cortex was removed in a microtome and incubated in a collagenase solution (0.05%) at 37° C. for 15 minutes. A tissue suspension was centrifuged and rinsed twice with 0.01% soybean trypsin inhibitor-solution (Gibco Laboratories, Grand Island, N.Y., USA) and a concentrate of PCT fragments and PCT cells were plated onto glass cover slips. The cells were cultured in Dulbecco's Modified Eagle's Medium [DMEM, 20 mmol/l 4-(2-hydroxyethyl)-1-piperazineethane sulphoric acid (Hepes), 24 mmol/l NaHCO₃ 50,000 IU/l penicillin and 50 mg/l streptomycin, pH 7.4] with 10% fetal bovine serum (Gibco) in an incubator at 37° C. with 95% O₂, and 5% CO₂. After 28 hours in culture the medium was changed to DMEM with 1% fetal bovine serum. The cells were examined approximately 18-36 hours later.

The interaction between C-peptide and the cell surface of the tubule cells was recorded using fluorescence correlation spectroscopy (11). Using a C-peptide concentration of 5 nM 92% of the peptide was found to be bound to the cell surface within 50 minutes. In contrast, when the cells were preincubated with 5 μM of Peptide E, C-peptide binding after 50 minutes was no more than 12%. Likewise, when C-peptide had been bound to the cells for 50 minutes and Peptide E was added afterwards, this resulted in dislocation of a major proportion of the C-peptide from its binding site within 4 hours; only 14% remained bound. Similar conditions obtained for peptide F. The results indicate that the peptides—in similarity to C-peptide—bind to a specific binding site on the cell surface.

REFERENCES

1. Biochemical Basis of Microvascular Disease, C. J. Mullarkey and M. Brownlee, p 534-545, in Textbook of Diabetes, Volume 2, editors J. Pickup and G. Williams. Blackwell, Oxford 1991.

2. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus, DCCT group. N Engl J Med 1993; 329: 977-983.

3. K. Kjeldsen, H. Brandgaard, P. Sidenius, J. Stenfatt Larsen and A. Nergaard. Diabetes decreases Na⁺K pump concentration in skeletal muscles, heart ventricular muscle, and peripheral nerves of rat. Diabetes 1987; 36: 842-848.

4. L. C. MacGregor and F. M. Matschinsky. Experimental diabetes impairs the function of the retinal pigmented epithelium. Metab Clin Exp 1986; 35: suppl 1, 28-34.

5. D. A. Greene and S. A. Lattimer. Impaired rat sciatic nerve sodium potassium adenosine triphosphatase in acute streptozocin diabetes and its correction by dietary myo-inositol supplementation. J Clin Invest 1983; 72: 1058-1063.

6. T. Clausen and M. E. Everts. Regulation of the Na,K-pump in skeletal muscle. Kidney International 1989; 35: 1-13.

7. Y. Ohtomo, A. Aperia, B. L. Johansson and J, Wahren. C-peptide stimulates renal Na⁺K⁺ATPase activity in synergism with neuropeptide Y. Diabetologia 1996; 39: 199-205.

8. T. Clackson and J. Wells. In vitro selection from protein and peptide libraries. Trends in Biotechnology 1995, 12: 173-184.

9. H. Nakanishi, S Ramurthy, A. Raktabutr, R. Shen and M. Eahn. Peptidomimetics of the immunoglobulin supergene family—a review. Gene 1993, 137: 51-56.

10. T. Kieber-Emons, R. Murali and M. I. Greene. Therapeutic peptides and peptidomimetics. Current Opinion in Biotechnology 1997, 8: 435-441.

11. R. Rigler. Journal of Biotechnology 1995, 41: 177-186.

                   #             SEQUENCE LISTING <160> NUMBER OF SEQ ID NOS: 14 <210> SEQ ID NO 1 <211> LENGTH: 31 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 1 Glu Ala Glu Asp Leu Gln Val Gly Gln Val Gl #u Leu Gly Gly Gly Pro   1               5  #                 10  #                 15 Gly Ala Gly Ser Leu Gln Pro Leu Ala Leu Gl #u Gly Ser Leu Gln              20      #             25      #             30 <210> SEQ ID NO 2 <211> LENGTH: 9 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 2 Glu Leu Gly Gly Gly Pro Gly Ala Gly   1               5 <210> SEQ ID NO 3 <211> LENGTH: 5 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 3 Glu Gly Ser Leu Gln   1               5 <210> SEQ ID NO 4 <211> LENGTH: 4 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 4 Glu Leu Gly Gly   1 <210> SEQ ID NO 5 <211> LENGTH: 6 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 5 Glu Leu Gly Gly Gly Pro   1               5 <210> SEQ ID NO 6 <211> LENGTH: 5 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 6 Gly Gly Pro Gly Ala   1               5 <210> SEQ ID NO 7 <211> LENGTH: 4 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 7 Gly Ser Leu Gln   1 <210> SEQ ID NO 8 <211> LENGTH: 7 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 8 Gly Gly Gly Pro Gly Ala Gly   1               5 <210> SEQ ID NO 9 <211> LENGTH: 5 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 9 Gly Gly Gly Pro Gly   1               5 <210> SEQ ID NO 10 <211> LENGTH: 4 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 10 Gly Gly Gly Pro   1 <210> SEQ ID NO 11 <211> LENGTH: 4 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 11 Gly Gly Pro Gly   1 <210> SEQ ID NO 12 <211> LENGTH: 8 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 12 Leu Ala Leu Glu Gly Ser Leu Gln   1               5 <210> SEQ ID NO 13 <211> LENGTH: 7 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 13 Ala Leu Glu Gly Ser Leu Gln   1               5 <210> SEQ ID NO 14 <211> LENGTH: 6 <212> TYPE: PRT <213> ORGANISM: Homo sapiens <400> SEQUENCE: 14 Leu Glu Gly Ser Leu Gln   1               5 

What is claimed is:
 1. A pharmaceutical composition comprising a peptide that (a) comprises the sequence EGSLQ (SEQ ID NO:3), (b) is up to 15 amino acids in length, and (c) has the ability to stimulate Na⁺K⁺ATPase activity.
 2. The pharmaceutical composition of claim 1, wherein the peptide is up to 10 amino acids in length.
 3. The pharmaceutical composition of claim 1, further comprising at least one additional active agent effective to treat Type I diabetes or a complication thereof.
 4. The pharmaceutical composition of claim 3, wherein the additional active agent is insulin.
 5. The pharmaceutical composition of claim 1, wherein the sequence of the peptide consists of EGSLQ (SEQ ID NO: 3).
 6. The pharmaceutical composition of claim 1, wherein the sequence of the peptide is selected from the group consisting of: LALEGSLQ (SEQ ID NO:12), ALEGSLQ (SEQ ID NO: 13) and LEGSLQ (SEQ ID NO: 14).
 7. The pharmaceutical composition of claim 1, wherein at least one amino acid of the up to ten amino acids N-terminally flanking EGSLQ in the peptide is different from the amino acid in the corresponding position in native human insulin C-peptide.
 8. The pharmaceutical composition of claim 7, wherein the peptide is up to 10 amino acids in length.
 9. The pharmaceutical composition of claim 7, further comprising at least one additional active agent effective to treat Type I diabetes complication thereof.
 10. The pharmaceutical composition of claim 9, wherein the additional active agent is insulin.
 11. A substantially isolated peptide, the sequence of which consists of EGSLQ (SEQ ID NO: 3).
 12. A method of treating diabetes or its complications, or stimulating Na⁺K⁺ATPase activity in a human or non-human subject, comprising (a) identifying a subject in need of treatment for diabetes or its complications, and (b) administering to the subject a pharmaceutical composition comprising the peptide of claim 11, wherein administration of the pharmaceutical composition treats diabetes or its complications, or stimulates Na⁺K⁺ATPase activity.
 13. A method of treating Type I diabetes or its complications, or stimulating Na⁺K⁺ATPase activity in a human or non-human subject, comprising (a) identifying a subject in need of treatment for Type I diabetes or its complications, and (b) administering the pharmaceutical composition of claim 1 to the subject, wherein administration of the composition treats diabetes or diabetic complications, or stimulates Na⁺K⁺ATPase activity.
 14. The method of claim 13, wherein the peptide is LALEGSLQ (SEQ ID NO: 12).
 15. The method of claim 13, wherein the peptide is ALEGSLQ (SEQ ID NO: 13).
 16. The method of claim 13, wherein the peptide is LEGSLQ (SEQ ID NO: 14).
 17. The method of claim 13, further comprising administering insulin to the subject.
 18. The method of claim 13, wherein the pharmaceutical composition is administered orally.
 19. A pharmaceutical composition comprising a peptide of up to 15 amino acids in length that is a fragment of the human insulin C-peptide, said peptide comprising the sequence EGSLQ (SEQ ID NO: 3), and having the ability to stimulate Na⁺K⁺ATPase activity.
 20. A method of treating Type I diabetes or its complications, or stimulating Na⁺K⁺ATPase activity in a human or non-human subject, comprising (a) identifying a subject in need of treatment for Type I diabetes or its complications, and (b) administering the pharmaceutical composition of claim 19 the subject, wherein administration of the composition treats diabetes or diabetic complications, or stimulates Na⁺K⁺ATPase activity.
 21. The method of claim 20, further comprising administering insulin to the subject.
 22. The method of claim 20, wherein the pharmaceutical composition is administered orally.
 23. The method of claim 20, further comprising administering insulin to the subject.
 24. The method of claim 20, wherein the pharmaceutical composition is administered orally.
 25. The pharmaceutical composition of claim 19, wherein the peptide is up to 10 amino acids in length.
 26. The pharmaceutical composition of claim 19, further comprising at least one additional active agent effective to treat Type I diabetes or a complication thereof.
 27. The pharmaceutical composition of claim 26, wherein the additional active agent is insulin. 